Nickel base alloy



Patented Mar. 2, 1937 PATENT oFFics NICKEL BASE ALLOY John T. Acker, Queens Village,'N. Y., and James R.-Wilson, Mountain Lakes, N. J., assig'nors to Bell Telephone Laboratories, Incorporated,- New York, N. Y., a corporation of New York Nb Drawing. Application June 25, 1936, Serial No. 87,220

4 Claims. (o1. 75-110) This invention relates to nickel base alloys particularly for use as an element of an electron emitting cathode of the oxide coated type which serves as an electrode in a discharge device.

This is a continuation-in-part of our copendingapplication, Serial No. 730,462,'filed June 13, 1934.

In recent years, nickel has largely superseded the more expensive .metals in the fabrication of cathodes for the emission of electrons in electron discharge devices, such as as high vacuum tubes,

gaseous discharge tubes and glow lamps. Usually, when nickel is the base or core of the emitting electrode, electron emitting material, such as oxides and metals of alkaline earth are associated with it either combined with the core or coated on the core in an uncombined state.

' As set forth in the above application, certain drawbacks preclude the use of pure nickel for specific purposes and the alloys proposed therein increase the strength, resistivity and efliciency of the cathode and substantially eliminate peeling 1 or flaking of the coating material from the base or core on which it is deposited.

Theobject of this invention is to attain the 5 desired resistivity and absence of flaking in cathodes and toincrease the operating efliciency of oxide-coated emitters. I

In accordance with this invention, which pertains to alloys for electron emittingicathodes of 30 suflicient mass to withstand tensile stress or to cathodes of'inherent strength. such as equi-potential emitters, it has been found that cobalt when alloyed with nickel increases the resistivity and the incorporation of carbon in the alloy enhances 5 the electron emission of a core or base coated with active material and, furthermore, the operating life is greatly increased.

Such alloys consist primarily of the ternary elements of nickel, cobalt and carbon in which the 40 nickel predominates. Suitable parameters for the constituents of the alloys are: nickel 70 to 90 per cent, carbon 0.1 to-1.5 per cent and the balance cobalt.- The alloys exhibit a completev absence of flaking or peeling when coated with 45 thermionically active material due, no doubt, to the elimination of deleterious metals which tend to' form an oxide interface between the base and the coating. This oxide interface is incapable of combining with. the emissive coating material and 50 consequent inadhesion of the coating results. v

A more limited group of parameters for the constituents of the alloy are nickel,84 to 85 per cent, cobalt 1 to 15 per cent and carbon .10 to .50 per cent. 55 In accordance with one example of a more spe cific aspect of the invention, the nickel base alloy consists of a melt of approximately 85 per cent nickel, 14.5 per cent cobalt and substantially .5 per cent carbon. Such a composition is desirable where strength is not of prime importance, such 5 as a sleeve cathode which is heated by conduction or radiation or a large filament where the crosssection is-ample to take care of the mechanical retemperature, based on area of core, was' 1.? watts "20 per square centimeter and approximately 1.18 watts'per square centimeter, based on the area of coating and core. The resistivity at the operating power was about 54.7 microhms centimeters. The thermionic efliciency was about 625 milliamperes per watt at the operating temperature after operating about 6,000 hours. This filament likewise proved to be free from peeling of the coating and represents an alloy composition which is desirable for an indirectly heated cathode wherestrength is not the controlling factor since this type of cathode has considerable mass as compared to a low ampere type filament.

It is apparent from the foregoing that tre-' mendous changes can be made in the characteristics of cathodes by a systematic change in the core alloys to produce a series of alloys which will meet vacuum tube requirements in a definite range of operating temperatures which will have 40 the added characteristic of coalescence or adherence of the active coating to the core and eliminate the faults heretofore encountered with nickel or nickel alloys that have been proposed heretofore to increase the strength and specific resistance of nickel.

While the main purpose of this invention is to set forth the characteristics of the nickel base alloys with respect to their operation as a core or base for an electron emitting coating which is maintainedin a state of incandescence, it is apparent that the alloys may form the base for other cathodes, such as a cold cathode in a glow discharge device. Furthermore, the alloys Of this invention may be suitable in other fields of application, such as resistance wire 3. A nickel base alloy consisting of nickel 84 heaters or as other electrodes in a discharge deto 85 per cent, cobalt approximately 15 per cent,

vice, such as the grid or anode. and carbon .13 per cent. I What is claimed is: 4. An' alloy core for an electron emitter con- 1. A nickel base alloy consisting of nickel sisting of substantially 85 per cent nickel, 14.5 5 from 70 to 90 per cent, carbon .1 to 1.5 per cent, per cent cobalt, and carbon .5 per cent.

and the balance cobalt.

2. A nickel base alloy consisting of nickel 84 OHN T. ACKER- to 85 per cent, cobalt approximately 15 per cent, JAMES R. WILSON.

and carbon .3 per cent. 

